The present invention is directed to a process for making fiber-reinforced structure, and more particularly to a method of manufacturing a cement board incorporating recycled carpet fiber.
Various techniques are presently available for making cement boards, as illustrated in U.S. Pat. Nos. Re. 271,109; 3,972,972; 4,668,548; 4,856,754; 5,787,597; 5,078,937; 5,724,783; 5,139,722; and 5,729,936. In particular, U.S. Re. Pat. No. 27,109 to Viden discloses a method and apparatus for producing special surfaces on panel board wherein the surface layer is simultaneously doctored onto a lower carrying layer and provided with an irregular top surface by a rotating roll arranged at an angle to the movement of the carrier material.
U.S. Pat. No. 3,972,972 to Yano et al. discloses a process of continuously producing a board of cement-like material reinforced by fibrous material wherein a granular mixture of the cement-like material and fibrous material is formed into a board under compression, and optionally with the addition of water.
U.S. Pat. No. 4,668,548 to Lankard discloses a method of producing a concrete overlay by drilling anchor holes in the concrete and placing a layer of fibers on the exposed surface and infiltrating a flowable cement slurry throughout the fibers and into the integral holes. Curing the slurry procedures an overlay with integral fiber-reinforced anchor portions.
U.S. Pat. No. 4,856,754 to Yokota et al. discloses a shuttering for forming concrete which includes a plate with a plurality of through holes openings on both its face and reverse, and double woven fabric consisting of a face tissue that permits passages of water, but prevents concrete from passing in the reverse tissue opposed to the face of the plate.
U.S. Pat. No. 4,787,597 to Yokota et al. discloses concrete forms including a first cloth sheet permitting surplus water and air contained in concrete cast in the form to pass therethrough but capable of blocking the passage of concrete, a second cloth sheet permeably secured to the first sheet permitting the surplus water and air to pass between and through the first and second sheets and to be absorbed into the second sheet as well as the first sheet and a support plate.
U.S. Pat. No. 5,078,927 to Eela discloses a method and system for producing a slab-like product in which a fibrous material is mixed with a settable material. The blank shaping units of the system are provided with stud-like material dispersing members.
U.S. Pat. No. 5,724,783 to Mandish discloses a panel manufactured by using Portland cement and waste aggregate materials, including used fiberglass insulation, recycled polystyrene, rubber tires, and old carpet material.
U.S. Pat. No. 5,139,722 to Lawton discloses pressing wet concrete between a ram and a mold to compact the concrete and express water from it so as to produce a molded slab. A layer of filter material is provided between the ram or the base of the mold and the concrete, and the filter material is secured by a discontinuous coat of adhesive applied as a transfer to the ram and/or to the base of the mold.
U.S. Pat. No. 5,729,936 to Maxwell discloses forming prefabricated panels by compressing a fiber slurry which may be composed of waste fiber products such as waste paper, cardboard, straw, leaves and grass clippings.
In conventional techniques, an attempt is made to add the fiber to the mortar during the final stages of the preparation of the mortar, i.e., after all of the constituents of the mortar have been worked into a fine paste. However, the fiber xe2x80x9cballs-upxe2x80x9d to some extent as it is wetted by the mortar. These fiber balls appear in varying amounts making it impossible to incorporate the fiber into the mixture and making it impossible to ensure that the fiber is uniformly distributed throughout the mortar mixture. Any blade or whisk system used after the fiber is added, ends up matted with fibers that may have wrapped around the mixing elements, such as the blade or wire, when the mixture is rotated. Drum mixing typically rolls the fiber into clumps, in much the same way as a rotary pelletizer operates to make pellets or balls. The rotating drum mixer cannot consistently produce uniform blending of the fiber and mortar.
In summary, the present techniques are not satisfactory in that they do not properly mix the fluid mortar into a tangled mat of fiber to thereby produce a board that does not have air-filled voids or have an irregular or rough surface.
In view of the above, there is a need in the industry for a technique that produces a strong cement board using recycled carpet fiber as a reinforcement material.
An object of the present invention is to provide a method of manufacturing a cement board incorporating recycled carpet fiber which produces a strong cement board even with a fluid mortar because the process specifies the use of a high-range water reducing agent to minimize the amount of water that is used, and further includes a step in which the fiber-mortar mixture is pressed between layers of filter fabric to assure that any problem of excess water is eliminated.
Another object of the present invention is to provide a method of manufacturing a cement board incorporating recycled carpet fiber in which the problem of air-filled voids or xe2x80x9cbugholesxe2x80x9d, that might produce an irregular, rough surface on the finished cement board, is eliminated.
Yet another object of the present invention is to provide a method of manufacturing a cement board incorporating recycled carpet fiber which produces a cement board with smooth surface.
Still yet another object of the present invention is to provide a method of manufacturing a cement board incorporating recycled carpet fiber which produces a uniform mixture of mortar and fiber from tangled recycled fibers, such as processed post-consumer carpet materials.
A further object of the present invention is to provide a method of manufacturing a cement board incorporating recycled carpet fiber wherein the use of tangled fibers produces a cement board in which the fiber has high pull-out resistance compared to the conventional short discrete fiber materials used in most concrete reinforcement applications.
Yet a further object of the present invention is to provide a method of manufacturing a cement board incorporating recycled carpet fiber in which the mixed fiber and mortar can be placed as a discrete layer thereby making it possible to make a cement board that has two exterior layers containing fiber and a central layer containing only mortar. This construction places the fiber reinforcement in a location in the cement board where it is needed to resist flexure.
Still yet a further object of the present invention is to provide a method of manufacturing a cement board incorporating recycled carpet fiber which utilizes comb-type mixing to incorporate a Portland cement-based mortar into a tangled mass of fiber.
In accordance with the present invention, a method of manufacturing a cement board includes providing an open mat of recycled carpet fibers in a container, placing the mortar mixture directly over the fiber mat, distributing the mortar through the fiber mat by moving a comb through the mortar-fiber mixture, and vibrating the mortar-fiber substantially simultaneously with the distribution of mortar through the fiber.